A road milling machine includes a milling drum with a plurality of cutter teeth mounted thereon which is contained within a milling enclosure or chamber. The milling machine is adapted to be advanced across a road surface to “mill” the surface to remove asphaltic or Portland cement concrete road pavement in preparation for recycling the pavement and/or in preparation for applying a pavement overlay. Road milling machines can also be used to “profile” or make smooth an asphalt or concrete road surface. The typical milling machine includes one or more conveyors to take the milled material from the vicinity of the milling drum and direct it away from the machine and into an adjacent dump truck. A road stabilizer/reclaimer machine is similar to a milling machine in that it comprises a wheeled or track-driven vehicle that includes a milling drum with a plurality of cutter teeth mounted thereon which is contained within a milling enclosure or chamber. However, the milling drum of a road stabilizer/reclaimer machine is generally employed to mill or pulverized an existing road bed or roadway to a greater depth than does a milling machine prior to repaving (usually called reclaiming) or prior to initial paving (usually called stabilizing), and it leaves the pulverized material in place. During the operation of a milling machine or a road stabilizer/reclaimer machine, the surface pavement is broken by the cutter teeth of the milling drum, thereby generating dust in the milling chamber.
The cutter teeth on the milling drum of a milling machine or a road stabilizer/reclaimer machine are typically made of metallic carbides or other very hard materials. As these teeth are forced through the road surface as the milling drum is rotated, they are heated by friction to a high temperature. A water spray bar with nozzles is typically mounted within or adjacent to the milling chamber to direct water to cool the hot cutter teeth and/or to control dust emissions. When this cooling water hits the cutter teeth, some of the water is turned into steam. The change in phase of water to steam creates volumetric expansion, and some of the dust and gas stream contents of the milling chamber can be blown out through gaps between the milling chamber and the road surface. Some of the dust that is blown out of or escapes the milling chamber of a milling machine or a road stabilizer/reclaimer machine can contain silica, which in certain forms comprises a health concern for the machine operators and other nearby personnel. To minimize or prevent the escape of the particulate silica and other dust from the milling chamber, it is known to equip the working machine with an emission control system. In some such systems, the dust and its entraining gas stream are routed to an area of safe discharge or to a dust separation device such as a filter assembly where the dust is separated from the entraining gas stream. In some such systems, the milling chamber is placed under a negative pressure using a fan device.
The critical importance of the temperature of the gas stream that contains water in a vapor (gaseous) state and dust generated during milling of a roadway for the efficient operation of an emission control system has not been appreciated. If the temperature of the gas stream is not high enough, the temperature of the gaseous water vapor in the gas stream may fall below its dew point so that the water vapor will condense to a liquid state. This can lead to mudding and fouling of ductwork and to mudding and fouling of separation and filtering devices such as cartridge filters, cyclones, baghouses and other devices. It would be advantageous if a method and apparatus could be developed for control of the temperature of the gas stream entraining dust generated during the milling of a roadway to insure efficient operation of an associated emission control system. Although the invention described herein may be employed in connection with an emission control system including a dust collection device in a working machine such as a milling machine or a road stabilizer/reclaimer machine, it may also be employed in connection with emission control systems with no dust collection device.
Notes on Construction
The use of the terms “a”, “an”, “the” and similar terms in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The terms “substantially”, “generally” and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. The use of such terms in describing a physical or functional characteristic of the invention is not intended to limit such characteristic to the absolute value which the term modifies, but rather to provide an approximation of the value of such physical or functional characteristic. All methods described herein can be performed in any suitable order unless otherwise specified herein or clearly indicated by context.
The use of any and all examples or exemplary language (e.g., “such as” and “preferably”) herein is intended merely to better illuminate the invention and the preferred embodiments thereof, and not to place a limitation on the scope of the invention. Nothing in the specification should be construed as indicating any element as essential to the practice of the invention unless so stated with specificity.
Various terms are specifically defined herein. These terms are to be given their broadest possible construction consistent with such definitions, as follows:
The term “water” refers to a fluid that is primarily or wholly comprised of water or a solution, emulsion or mixture in which water is the primary component.
The terms “steam”, “water vapor”, “vapor” and similar terms refer to water in a gaseous state.
The term “gas stream” refers to a stream or flow of a gas which may include air and water vapor.
The term “dust” refers to particulate material that can be entrained in a gas stream.
The term “working machine” refers to a milling machine and/or a stabilizer/reclaimer machine and/or any other road working machine that includes a milling drum and a spray assembly for use in dispensing water for heat and/or dust control.
The terms “upper”, “top” and similar terms, when used in reference to a relative position or direction on or with respect to a working machine, or a component or portion of such a machine, refer to a relative position or direction that is farther away from the surface on which the working machine is placed for operation.
The terms “lower”, “bottom” and similar terms, when used in reference to a relative position or direction on or with respect to a working machine, or a component or portion of such a machine, refer to a relative position or direction that is nearer to the surface on which the working machine is placed for operation.
The term “front end” and similar terms, when used in connection with a working machine or a component or portion of such a machine, refer to the end of the machine, or the component or portion thereof which is in the direction of travel of the machine while it is being operated.
The terms “forward”, “in front of”, and similar terms, as used herein to describe a relative position or direction on or in connection with a working machine, or a component or portion of such a machine, refer to a relative position or direction towards the front end of the machine.
The terms “back end”, “rear end” and similar terms, when used in connection with a working machine or a component or portion of such a machine, refer to the end of the machine or the component or portion thereof which is farther from the front end of the working machine.
The terms “rearward”, “behind”, and similar terms, as used herein to describe a relative position or direction on or in connection with a working machine, or a component or portion of such a machine, refer to a relative position or direction towards the rear end of the machine.
The term “linear actuator” refers to an electric, hydraulic, electro-hydraulic or mechanical device that generates force which is directed in a straight line. One common example of a “linear actuator” is a hydraulic actuator which includes a cylinder, a piston within the cylinder, and a rod attached to the piston. By increasing the pressure within the cylinder on one side of the piston (over that on the opposite side of the piston), the rod will extend from the cylinder or retract into the cylinder.
The term “rotary actuator” refers to an electric, hydraulic or electro-hydraulic motor or other device that generates force that is directed along an arc or about a center of rotation.
The term “actuator” refers to a linear actuator or a rotary actuator.